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Collision‐induced dissociation of protonated MK‐0991: novel ring opening of a cyclic hexapeptide in the gas phase
Author(s) -
Qin XueZhi,
Wu Yunhui,
Zhao Zack,
Chen Xin
Publication year - 1999
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199907)34:7<733::aid-jms824>3.0.co;2-j
Subject(s) - chemistry , protonation , cyclic peptide , electrospray ionization , stereochemistry , tandem mass spectrometry , peptide , ethylenediamine , dissociation (chemistry) , mass spectrum , mass spectrometry , ion , organic chemistry , chromatography , biochemistry
Electrospray ionization tandem mass spectrometry was applied to probe the collision‐induced dissociation (CID) of protonated MK‐0991 {(4 R ,5 S )‐5‐[(2‐aminoethyl)amino]‐ N 2 ‐(10,12‐dimethyl‐1‐oxotetradecyl)‐4‐hydroxy‐ L ‐ornithyl‐ L ‐threonyl‐ trans ‐4‐hydroxy‐ L ‐prolyl‐( S )‐4‐hydroxy‐(4‐hydroxyphenyl)‐ L ‐threonyl‐ threo ‐3‐hydroxy‐ L ‐or‐nithyl‐ trans ‐3‐hydroxy‐ L ‐proline cyclic (6–1)‐peptide} in the gas phase; MK‐0991 is a newly developed, broad‐spectrum pneumocandin antifungal drug. The study showed that protonated MK‐0991 ( m / z 1094) undergoes specific ring opening under the CID conditions to form two protonated linear peptides at m / z 1076 and 1034. This is different from the commonly observed ring opening of a cyclic peptide that occurs by the cleavage of the N ‐acyl bonds in many places on the peptide backbone. The structures of the two linear peptides were elucidated on the basis of their tandem mass spectra. The results strongly indicate that the specific ring opening of MK‐0991 is affected by the ethylenediamine side‐chain formed from the modification of one of the ornithine amino acids in this cyclic hexapeptide. Copyright © 1999 John Wiley & Sons, Ltd.